Separating solids from liquids in a drilling fluid

ABSTRACT

Techniques for separating cuttings from liquid include circulating a drilling fluid that comprises a liquid and formation cuttings to a scree of a screen assembly that includes screen sections; vibrating the screen assembly during circulation of the drilling fluid; while vibrating the screen assembly, separating the liquid from the plurality of formation cuttings; while vibrating the screen assembly, separating a first portion of the formation cuttings of a first size from the drilling fluid with a first screen section; rotating the screen assembly; subsequent to rotating the screen assembly and while vibrating the screen assembly, separating a second portion of the formation cuttings of a second size different than the first size from the drilling fluid with a second screen section; directing the separated liquid through the screen assembly to a liquid outlet; and directing at least one of the first or second portions of the formation cuttings to a cuttings outlet formed in the screen.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of and claims priority to U.S. patentapplication Ser. No. 16/879,273, filed on May 20, 2020, the entirecontents of which is incorporated by reference herein.

TECHNICAL FIELD

This disclosure relates to separating solids from liquids in a drillingfluid.

BACKGROUND

In drilling and workover operations, drilling fluid (often called“drilling mud”) is used to keep a hydrostatic pressure within a wellborewhile drilling or while work over by circulating the drilling fluid intothe wellbore. For example, the drilling fluid may be circulated througha tubular work string or drill pipe and through one or more nozzlesformed in the drill bit and out into the wellbore. The drilling fluidhelps with well control, as well as carries cuttings removed from asubterranean formation by the drill bit during drilling the wellboreback to the surface. These cuttings can be separated from the drillingfluid to maintain an initial set of properties (for example, viscosity,density, gel strength) of the drilling fluid.

SUMMARY

This disclosure describes implementations of a shaker screen system thatmay be used to separate formation cuttings from a liquid in a drillingfluid that has been used and recovered from a wellbore drilling orworkover operation. In some aspects, the shaker screen system includes ascreen assembly that includes multiple screen sections attached orcoupled together (for example, within a circular screen). In someaspects, one or more of the multiple screen sections are formed ofscreens with varying mesh sizes, thereby allowing cuttings of differentsizes to pass through the one or more screen sections.

In an example implementation, a drilling fluid shaker screen systemincludes a screen assembly that includes a screen mounted to a funnel,the screen including a plurality of screen sections. A first screensection of the plurality of screen sections includes a first screen meshsize and a second screen section of the plurality of screen sectionsincludes a second screen mesh size different than the first screen meshsize. The first and second screen mesh sizes are based at least in parton a size of one or more cuttings entrained in a drilling fluid used ina drilling or workover operation. The drilling fluid shaker screensystem further includes a rotation assembly mounted to the screenassembly. The rotation assembly includes one or more rollers moveable torotate the screen assembly about an axis of rotation. The drilling fluidshaker screen system further includes a motor assembly coupled to thescreen assembly and configured to vibrate the screen assembly; and ahousing coupled to the screen assembly and the rotation assembly. Thehousing includes a cuttings outlet that is fluidly coupled to a cuttingsinlet formed in the screen and a liquid outlet separate from thecuttings outlet that is fluidly coupled to the plurality of screensections.

In an aspect combinable with the example implementation, the screenincludes a circular screen area, and each of the plurality of screensections includes a co-equal portion of the circular screen area.

In another aspect combinable with any of the previous aspects, theplurality of screen sections include four screen sections that includethe first and second screen sections, each of the four screen sectionsincluding a quarter of the circular screen area.

In another aspect combinable with any of the previous aspects, the fourscreen sections further include a third screen section that includes athird screen mesh size and a fourth screen section that includes afourth screen mesh size.

In another aspect combinable with any of the previous aspects, each ofthe first, second, third, and fourth screen mesh sizes is different.

In another aspect combinable with any of the previous aspects, thescreen is mounted to the funnel at an angle that slopes downward from aperimeter of the screen toward the cuttings inlet.

In another aspect combinable with any of the previous aspects, therotation assembly includes at least one rail mounted to at least one ofthe screen assembly or the rotation assembly and adjacent a perimeter ofthe screen assembly.

In another aspect combinable with any of the previous aspects, the railis configured to receive at least a portion of the one or more rollers.

Another aspect combinable with any of the previous aspects furtherincludes a vibration assembly mounted to the housing and including oneor more springs configured to oscillate the screen assembly based atleast in part on operation of the motor assembly.

In another aspect combinable with any of the previous aspects, thevibration assembly is mounted to a bottom portion of the rotationassembly, and the rotation assembly is mounted to a bottom portion ofthe funnel.

Another aspect combinable with any of the previous aspects furtherincludes a locking assembly that includes a first member attached to thescreen assembly; a second member attached to the rotation assembly; abore formed through each of the first and second members; and a pininsertable through the bore to fixedly lock the screen assembly to therotation assembly.

In another aspect combinable with any of the previous aspects, the firstscreen mesh size is configured to allow a first cutting to pass therethrough, and the second screen mesh size is configured to allow a secondcutting larger than the first cutting to pass there through.

In another aspect combinable with any of the previous aspects, thecuttings inlet includes a hole in the screen centered at a center of thescreen assembly.

In another aspect combinable with any of the previous aspects, thehousing defines an interior volume fluidly coupled to the liquid outlet.

In another example implementation, a method for separating cuttings fromliquid in a drilling fluid includes circulating a drilling fluid thatincludes a liquid and a plurality of formation cuttings to a screenassembly that includes a screen, the screen including a plurality ofscreen sections; vibrating the screen assembly during circulation of thedrilling fluid to the screen assembly; while vibrating the screenassembly, separating, with the screen assembly, the liquid from theplurality of formation cuttings; while vibrating the screen assembly,separating a first portion of the plurality of formation cuttings of afirst size from the drilling fluid with a first screen section thatincludes a first screen mesh size; rotating the screen assembly;subsequent to rotating the screen assembly and while vibrating thescreen assembly, separating a second portion of the plurality offormation cuttings of a second size different than the first size fromthe drilling fluid with a second screen section that includes a secondscreen mesh size different than the first screen mesh size; directingthe separated liquid through the screen assembly to a liquid outlet; anddirecting at least one of the first or second portions of the pluralityof formation cuttings to a cuttings outlet formed in the screen.

In an aspect combinable with the example implementation, the screenincludes a circular screen area, and each of the plurality of screensections includes a co-equal portion of the circular screen area.

Another aspect combinable with any of the previous aspects furtherincludes further rotating the screen assembly; while vibrating thescreen assembly, separating a third portion of the plurality offormation cuttings of a third size different from the first and secondsizes from the drilling fluid with a third screen section that includesa third screen mesh size different than the first and second screen meshsizes; further rotating the screen assembly; and while vibrating thescreen assembly, separating a fourth portion of the plurality offormation cuttings of a fourth size different from the first, second,and third sizes from the drilling fluid with a fourth screen sectionthat includes a fourth screen mesh size different than the first,second, and third screen mesh sizes.

Another aspect combinable with any of the previous aspects furtherincludes directing at least one of the third or fourth portions of theplurality of formation cuttings through the screen assembly with theseparated liquid to the liquid outlet; and directing the other of the atleast one of the third or fourth portions of the plurality of formationcuttings to the cuttings outlet formed in the screen.

Another aspect combinable with any of the previous aspects furtherincludes directing the at least one of the first or second portions ofthe plurality of formation cuttings at a downward angle toward thecuttings inlet and away from a perimeter of the screen.

In another aspect combinable with any of the previous aspects, vibratingthe screen assembly includes operating a motor to drive a gear or wheelcoupled with the screen assembly; based on driving the gear or wheel,oscillating the screen assembly with a plurality of springs coupled tothe screen assembly.

In another aspect combinable with any of the previous aspects, rotatingthe screen assembly includes moving at least one roller coupled with thescreen assembly on a rail; and based on moving the at least one roller,rotating the screen assembly about an axis of rotation.

In another aspect combinable with any of the previous aspects, the firstscreen section that includes the first screen mesh size is positioned toreceive the drilling fluid that includes the liquid and the plurality offormation cuttings during separating the first portion of the pluralityof formation cuttings of the first size from the drilling fluid with thefirst screen section.

In another aspect combinable with any of the previous aspects, rotatingthe screen assembly includes rotating the screen assembly to positionthe second screen section that includes the second screen mesh size toreceive the drilling fluid that includes the liquid and the plurality offormation cuttings.

Another aspect combinable with any of the previous aspects furtherincludes prior to rotating the screen assembly, unlocking the screenassembly against rotation.

In another aspect combinable with any of the previous aspects, directingthe at least one of the first or second portions of the plurality offormation cuttings to the cuttings outlet formed in the screen includesdirecting the at least one of the first or second portions of theplurality of formation cuttings to the cuttings outlet that is centeredat a center of the screen assembly.

Another aspect combinable with any of the previous aspects furtherincludes directing at least a portion of the separated liquid throughthe screen assembly through the liquid outlet and to an enclosed portionof a housing that is coupled to the screen assembly.

Implementations of a shaker screen system according to the presentdisclosure may include one or more of the following features. Forexample, the shaker screen system may provide for multiple, differentscreens that each have a different screen mesh size in a singleassembly. As another example, the shaker screen system may moreefficiently remove unwanted fine particles as compared to conventionalshaker screens, which can save cost and rig time during a drilling orworkover operation. As another example, the shaker screen system mayallow for switching from one screen mesh size to another without theconventional requirement of stopping operations to remove and installscreens of different mesh size in the shaker screen system. As yetanother example, the shaker screen system may require less time (forexample, by an operator) to change to a desired screen mesh size.

The details of one or more implementations of the subject matterdescribed in this disclosure are set forth in the accompanying drawingsand the description below. Other features, aspects, and advantages ofthe subject matter will become apparent from the description, thedrawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of wellbore drilling or workover processthat includes a shaker screen system according to the presentdisclosure.

FIG. 2 is a schematic diagram of an example implementation of a shakerscreen system according to the present disclosure.

FIG. 3 is an exploded view of an example implementation of a shakerscreen system according to the present disclosure.

FIGS. 4A-4B are schematic illustrations of components of an exampleimplementation of a shaker screen system according to the presentdisclosure.

FIGS. 5-6 are schematic illustrations of one or more details of a screenassembly of an example implementation of a shaker screen systemaccording to the present disclosure.

FIG. 7 is a schematic illustration of a locking assembly of an exampleimplementation of a shaker screen system according to the presentdisclosure.

FIG. 8 is a partial schematic illustrations of a screen assembly of anexample implementation of a shaker screen system according to thepresent disclosure.

FIG. 9 is a flowchart that describes an example method for separatingformation cuttings from a liquid in a drilling fluid according to thepresent disclosure.

DETAILED DESCRIPTION

The present disclosure describes a shaker screen system that may be usedto separate formation cuttings from a liquid of a drilling fluid that isrecovered to a terranean surface from a wellbore in a drilling orworkover operation. In some aspects, the shaker screen system includes arotating screen, which allows multiple size mesh to be installed in onescreen to remove different size cuttings from a flow of the drillingfluid. Thus, in some aspects, the example implementations of the shakerscreen system may scale efficiently and be used to separate cuttingsfrom liquid in many different types of drilling fluid (for example,according to viscosity, density, or otherwise) as well as many differenttypes of subterranean formations (for example, shale, sandstone, orotherwise).

FIG. 1 is a schematic diagram of wellbore drilling or workover process10 (“drilling process 10”) that includes a shaker screen system 24according to the present disclosure. Generally, the drilling process 10represents a process in which a wellbore 14 is formed from a terraneansurface 17 and through one or more subterranean formations 18 by adrilling rig 12. The drilling process 10, in this example, includes adrill bit 16 coupled to a downhole conveyance (for example, a tubulardrill string, such as conventional or coiled tubing) that forms thewellbore 14 with a drilling fluid 20. The drilling fluid 20 is providedto the drill bit 16 by, for example, the downhole conveyance, andcirculates through the drill bit 16 during drilling of the wellbore 14in order to, for example, cool the drill bit 16 and removing cuttingsfrom the subterranean formation 18 back to the surface 17. Thus, returndrilling fluid 22 includes the drilling fluid 20 (for example, a wateror foam and chemical mixture) as well as cuttings (for example, bits ofrock cut from the formation 18 by the drill bit 16). Return drillingfluid 22, therefore, includes liquid 28 and cuttings 26 from theformation 18, which may be removed.

As shown in FIG. 1 , the return drilling fluid 22 is circulated out ofthe wellbore 14 to the shaker screen system 24. As described in moredetail in this disclosure, the shaker screen system 24 separates theliquid 28 from the cuttings 26 of the return drilling fluid 22 with ascreen that includes multiple screen sections. At least one of thescreen sections has a particular screen mesh size (for example, a sizeof the holes in the screen section) that is different than anotherparticular screen mesh size of another screen section of the screen.Thus, different sized cuttings 26 may be filtered by the shaker screensystem 24. Some cuttings 26 may be small enough to remain entrained inthe liquid 28. Other cuttings 26 may be large enough to be separatedfrom the liquid 28 by the shaker screen system 24.

As shown in the example implementation of FIG. 1 , the liquid 28 (whichmay include some cuttings 26 of a size small enough to remain entrainedin the liquid 28 through the shaker screen system 24) and the cuttings26 are separated into two separate streams. The liquid 28 is circulatedfrom the shaker screen system 24 in a fluid pathway 32 and into a mudtank 36. Generally, the mud tank 36 is used to hold the separated liquid28 and provide the separated liquid 28 as a source of liquid foradditional drilling fluid 20 (in other words, to recycle back into thedrilling process 10 as drilling fluid 20). The cuttings 26 arecirculated into a cuttings pathway 30 and into one or more waste pits34. Generally, the waste pits 34 are pits or other enclosures that storethe cuttings 26 for proper disposal.

FIG. 2 is a schematic diagram of an example implementation of a shakerscreen system 200 according to the present disclosure. The shaker screensystem 200, in this example, may be used as the shaker screen system 24shown in the drilling process 10 in FIG. 1 . FIG. 3 is an exploded viewof the example implementation of the shaker screen system 200. As shownin this implementation, the shaker screen system 200 includes a housing212 that forms a partial enclosure with an open top. A screen assembly202 is mounted to the open top of the housing 212 by legs 236 thatinsert into holes 252. The screen assembly 202, in this example,includes a screen 204 (for example, circular) that is comprised ofmultiple screen sections 206. In this example, there are four screensections 206 that combine to form the screen 204 in equal portions(here, quarter portions). Other implementations may include more orfewer screen sections 206.

Each of the multiple screen sections 206 may have a screen mesh sizethat is different than a screen mesh size of the other screen sections206. For example, as shown in FIGS. 2-3 , each of the four screensections 206 may have a screen mesh size different than the screen meshsize of the other screen sections 206. Thus, as the screen 204 rotatesduring operation of the shaker screen system 200, a particular screensection 206 of a particular screen mesh size will remove specificcuttings 26 of a specific particle size, and as the screen 204 continuesto rotate, the next screen section 206 of a different screen mesh sizewill remove, for example, even finer particles of cuttings 26. During afull rotation of the screen 204 (for example, 360° about the axis 248),the return drilling fluid 22 may be restored to the same or similarproperties (for example, viscosity, density) as the drilling fluid 20.

In this example, there are four different screen mesh sizes, which allowfor four differently-sized cuttings from a return drilling fluid to beseparated from the liquid in the return drilling fluid. In otherexamples, two of the four screen sections 206 may have a particularscreen mesh size and two of the four screen sections 206 may haveanother particular screen mesh size. In other examples, one of the fourscreen sections 206 may have a particular screen mesh size and three ofthe four screen sections 206 may have another particular screen meshsize. Other examples of different combinations of screen sections 206and screen mesh sizes are also contemplated by the present disclosure.

Turning briefly to FIG. 6 , the screen 204 is positioned at a top of afunnel 234 that includes the legs 236 that can be inserted into arotation assembly 208 that is mounted to the housing 212 below thescreen assembly 202. The funnel 234 and screen 204 include a cuttingsinlet 226 formed with a center that coincides with a centerline axis 248of the shaker screen system 200. Springs 238 are positioned about thelegs 236 in order for the screen assembly 202 to “float” on the rotationassembly 208.

Turning briefly to FIG. 8 , this figure shows a detail of the screenassembly 202. In this example implementation, the funnel 234 may beangled (for example, downward) at a particular angle. In this example,the angle is at or about 20°, but other angles are contemplated by thepresent disclosure. The screen 204 may also be angled from a perimeter227 of the screen 204 toward the cuttings inlet 226. In this example thescreen 204 may also be angled downward at or about 20°.

Turning briefly to FIG. 5 , a detail of the connection between thescreen assembly 202 and the rotation assembly 208 is shown. Asillustrated in this figure, the leg 236 is inserted into the hole 252 ofan upper plate 250 of the rotation assembly 208. The spring 238 buffetscontact between the screen assembly 202 and the rotation assembly 209.Once the leg 236 is positioned through the hole 252, a cotter pin 264may be positioned to secure the screen assembly 202 to the rotationassembly 209, as shown.

Turning back to FIGS. 2 and 3 , the rotation assembly 208 operates toprovide rotation 246 to the screen assembly 202, for example duringoperation of the shaker screen system 200 or between operation times ofthe shaker screen system 200. In this example, the rotation assembly 208includes one or more rails 242 (in this example, two, an upper rail 242and a lower rail 242) that circumscribe an inside perimeter of therotation assembly 208. One or more rollers 244 are mounted to the rails242 and are moved (for example, rotated) to rotate the rotation assembly208 and the screen assembly 202.

Turning briefly to FIGS. 4A-4B, these figures illustrate portions of therotation assembly 208. For example, as shown, in this example, the rails242 are attached to the upper plate 250 and a lower plate 258 of therotation assembly 208. The rails 242 are aligned along the perimeters ofthe lower and upper plates 258 and 250, respectively. A roller 244 isconnected, in this example, to the upper plate 250 through a leg 254 toreceive and ride on the rails 242 as shown. In operation, the rotationassembly 208 may be rotated in order to rotate the shaker screenassembly 202 into a position such that a particular screen section 206(with a particular screen mesh size) is positioned to receive the returndrilling fluid 22. As described with reference to FIG. 7 , for instance,once positioned appropriately, the shaker screen assembly 202 may belocked or otherwise held in place. If a different screen section 206(with different screen mesh size) is desired, the shaker screen assembly202 may be unlocked and rotated (on the rotation assembly 208) so that adifferent screen section 206 is positioned to receive the returndrilling fluid 22.

The example implementation of the shaker screen system 200 includes avibration assembly 210 mounted to or in the housing 212 below a rotationassembly 208. As shown in this example, the vibration assembly 210include multiple springs 214 that facilitate oscillation of the rotationassembly 208 (for example, vertical oscillation), which in turn istranslated to the screen assembly 202 during operation of the shakerscreen system 200. In this example implementation, a motor assembly 216may be operated (for example, by the controller 999) to providevibratory movement to initiate (and also, maintain, in some aspects)oscillation of the rotation assembly 208 (for example, verticaloscillation), which in turn is translated to the screen assembly 202during operation of the shaker screen system 200.

As shown, the motor assembly 216 includes an electric motor 232 coupledto a motor gear 218, that in turn is coupled to a drive gear 222 througha belt or chain 220. A control system (or controller) 999 iscommunicably coupled to the motor assembly 216 to control operations ofthe motor assembly 216. In example implementations, the controller 999may be a microprocessor-based, electro-mechanical, pneumatic, orhydraulic controller that may control the motor assembly 216 based onoperator input and/or based on a sensed operation of the motor assembly216, and more generally, the shaker screen system 200.

As shown in the example implementation of the shaker screen system 200,a cuttings pathway 224 extends vertically through the shaker screensystem 200, with the cuttings inlet 226 forming an inlet to the pathway224 and the pathway 224 having a cuttings outlet 228 formed opposite thecuttings inlet 226. As explained in more detail later, cuttings 26 fromthe return drilling fluid 22 that are not small enough to be entrainedwith the liquid 28 are separated from the return drilling fluid 22 andmove (for example, through vibration) to the cuttings inlet 226 and thenthrough the cuttings pathway 224 for removal from the outlet 228 (forexample, to one or more mud pits). In some examples, the cuttingspathway 224 is formed of a tubular that extends between the cuttingsinlet 226 and the cuttings outlet 228. Thus, once in the pathway 224,cuttings 26 may not escape into a liquid pathway 230 of the housing 212.

As further shown in this example, the liquid pathway 230 extendsvertically through the shaker screen system 200 in an annulus betweenthe cuttings pathway 224 and the housing 212. The liquid pathway 230includes an inlet 231 located under the screen 204 in order to receivethe separated liquid 28 from the return drilling fluid 22. In thisexample, the liquid pathway 230 include an outlet 240 to direct theliquid 28 to, for example, one or more mud tanks 36. As explained inmore detail later, liquid 28 (and small cuttings 26 entrained in theliquid 28) from the return drilling fluid 22 is separated from thereturn drilling fluid 22 and falls through the screen 204 into theliquid pathway 230. In some examples, the liquid pathway 230 is formedof a tubular that extends between the inlet 231 and a bottom of thehousing 212. Thus, once in the pathway 230, liquid 28 may not escapeinto an inner volume of the housing 212 or into the cuttings pathway224.

Turning to FIGS. 4B and 7 , these figures illustrate an exampleimplementation of a locking assembly 268 of the shaker screen system200. For example, during non-operation of the shaker screen system 200or, for example, to lock a particular screen section 206 (with a desiredscreen mesh size) at a desired location, the rotation assembly 208 maybe locked against rotational movement, thereby also locking the screenassembly 202 against rotational movement. As shown in this example, thelocking assembly 268 includes a plate 260 attached to the upper plate250 and a plate 260 attached to the lower plate 258. Each of the plates260 includes a bore 262 there through. When the plates 260 are aligned,the bores 262 of the plates 260 are aligned to accept a locking pin 266through the bores 262. The locking pin 266, once inserted through bothbores 262, locks the upper and lower plates 250 and 258 againstrotational movement, thereby preventing rotational movement of therotation assembly 208.

FIG. 9 is a flowchart that describes an example method 900 forseparating formation cuttings 26 from a liquid 28 in a return drillingfluid 22. The example method 900 is described with reference to theshaker screen system 200 shown in the figures. Method 900 may begin atstep 902, which includes circulating a drilling fluid of liquid andformation cuttings to a screen assembly that includes a screen ofmultiple screen sections. For example, return drilling fluid 22 may becirculated to the screen assembly 202 of the shaker screen system 200shown in the figures. The return drilling fluid 22 is comprised ofliquid 28 and cuttings 26. As shown in FIGS. 2-3 , the screen assembly202 includes multiple screen sections 206 of the screen 204. In someaspects, the screen sections 206 have differing screen mesh sizes toallow for different sizes of the particles in the cuttings 26 to fallthrough the mesh.

Method 900 may continue at step 904, which includes vibrating the screenassembly during circulation of the drilling fluid to the screenassembly. For example, as shown in FIGS. 2-3 , the motor assembly 216(for example, with electric motor 232 or other prime mover) may bestarted (and controlled by the controller 999) to vibrate the shakerassembly 200. The motor 232 drives the motor gear 218, which in turndrives the gear 222 through belt or chain 220. As the gear 222 rotates,the shaker screen assembly 202 vibrates. For example, oscillation of therotation assembly 208 (and likewise the screen assembly 202) may occurbased on the operation of the motor assembly 216 to initiate vibrationand also the springs 214 mounted below the rotation assembly 208. Insome aspects, initial operation of the motor assembly 216 may besufficient to begin (and maintain) oscillation of the assemblies 208 and202 by the springs 214. In some aspects, continual operation of themotor assembly 216 may be needed to begin (and maintain) oscillation ofthe assemblies 208 and 202 by the springs 214. In some aspects, theoscillation may be eccentric.

Method 900 may continue at step 906, which includes which includesseparating, with the screen assembly, the liquid from the formationcuttings. For example, as the return drilling fluid 22 is circulated tothe screen 204, the liquid 28 may be separated by failing through thescreen sections 206. The separated liquid 28 falls into the liquidpathway 230 and exits the housing 212 of the shaker screen system 200 atthe outlet 240 (for example, to the mud tank 36). In some aspects, aportion of the cuttings 26 may also be entrained in the liquid 28 andfall through the screen sections 206 into the liquid pathway 230. Forexample, one or more particular screen sections 206 may be selectedbased on or include a screen mesh size that allows certain sizeparticles to stay entrained with the liquid 28. As the screen assembly202 rotates and the particular screen sections 206 receive thecirculated return drilling fluid 22, such smaller particles may passthrough these screen sections 206.

Method 900 may continue at step 908, which includes separating a firstportion of the formation cuttings of a first size from the drillingfluid with a first screen section of a first screen mesh size. Forexample, particles larger than those entrained with the liquid 28 mayremain in the return drilling fluid 22 on the screen 204 until suchparticles are moved (for example, by vibration) to a first screensection 206 with a mesh size that allows the particles of the cuttings26 to fall there through (to the cuttings pathway 224). Other, largerparticles of the cuttings 26 may remain on the screen 204 as they do notfall through the first screen section 206.

Method 900 may continue at step 910, which includes directing theseparated liquid through the screen assembly to a liquid outlet. Forexample, the separated liquid 28 falls into the liquid pathway 230 andexits the housing 212 of the shaker screen system 200 at the outlet 240(for example, to the mud tank 36). In some aspects, of course, steps 908and 910 may be performed simultaneously or substantially simultaneously.

Method 900 may continue at step 912, which includes rotating the screenassembly. For example, in some aspects, the first screen section of thefirst screen mesh size may be desired to separate the formation cuttingsof the first size from the liquid. But as the return drilling fluid maychange consistency (for example, with different sized formation cuttingsdue to, for instance, a different rock formation). Thus, in someaspects, another screen mesh size (in a second screen section) may bedesired at some point during method 200. In some aspects, rotating thescreen assembly includes unlocking the rotation assembly 208 to allowrotation of the rotation assembly 208, and thus the shaker screenassembly 202, to move the desired shaker screen section 206 to receivethe return drilling fluid 22. Once rotated, the shaker screen assembly202 may be re-locked into position, for instance, by re-locking therotation assembly 208.

Method 900 may continue at step 914, which includes separating a secondportion of the formation cuttings of a second size different than thefirst size from the drilling fluid with a second screen section of asecond screen mesh size that is different than the first screen meshsize. For example, the larger particles that do not fall through thefirst screen section 206 of step 908 may nonetheless be moved (forexample, through vibration) to a second screen section 206 with a largermesh size (in other words, larger holes in the screen section) relativeto the first screen section 206 of step 908. Once the larger particlesof the cuttings 26 are moved to the second screen section 206, suchparticles may then fall through the second screen section 206 to thecuttings pathway 224. In additional aspects of method 900, steps 912 and914 may be repeated for each different screen mesh size of the differentscreen sections 206 of the screen 204.

Method 900 may continue at step 916, which includes directing theseparated liquid through the screen assembly (the second screen section)to the liquid outlet. For example, the separated liquid 28 falls intothe liquid pathway 230 and exits the housing 212 of the shaker screensystem 200 at the outlet 240 (for example, to the mud tank 36). In someaspects, of course, steps 914 and 916 may be performed simultaneously orsubstantially simultaneously.

Method 900 may continue at step 918, which includes directing at leastone of the first or second portions of the formation cuttings to acuttings inlet formed in the screen. For example, once the particles ofthe cuttings 26 fall through one of the first or second screen sections206, such particles may then enter the cuttings pathway 224 and exit thehousing 212 to the waste pits 34.

A number of implementations have been described. Nevertheless, it willbe understood that various modifications may be made without departingfrom the spirit and scope of the disclosure. For example, exampleoperations, methods, or processes described herein may include moresteps or fewer steps than those described. Further, the steps in suchexample operations, methods, or processes may be performed in differentsuccessions than that described or illustrated in the figures.Accordingly, other implementations are within the scope of the followingclaims.

What is claimed is:
 1. A method for separating cuttings from liquid in adrilling fluid, the method comprising: circulating a drilling fluid thatcomprises a liquid and a plurality of formation cuttings to a screenassembly that comprises a screen, the screen comprising a plurality ofscreen sections; vibrating the screen assembly during circulation of thedrilling fluid to the screen assembly; while vibrating the screenassembly, separating, with the screen assembly, the liquid from theplurality of formation cuttings; while vibrating the screen assembly,separating a first portion of the plurality of formation cuttings of afirst size from the drilling fluid with a first screen section thatcomprises a first screen mesh size; rotating the screen assembly, whererotating the screen assembly comprises: moving at least one rollercoupled with the screen assembly on a rail, and based on moving the atleast one roller, rotating the screen assembly about an axis ofrotation; subsequent to rotating the screen assembly and while vibratingthe screen assembly, separating a second portion of the plurality offormation cuttings of a second size different than the first size fromthe drilling fluid with a second screen section that comprises a secondscreen mesh size different than the first screen mesh size; directingthe separated liquid through the screen assembly to a liquid outlet; anddirecting at least one of the first or second portions of the pluralityof formation cuttings to a cuttings outlet formed in the screen.
 2. Themethod of claim 1, wherein the screen comprises a circular screen area,and each of the plurality of screen sections comprises a co-equalportion of the circular screen area.
 3. The method of claim 1, furthercomprising: further rotating the screen assembly; while vibrating thescreen assembly, separating a third portion of the plurality offormation cuttings of a third size different from the first and secondsizes from the drilling fluid with a third screen section that comprisesa third screen mesh size different than the first and second screen meshsizes; further rotating the screen assembly; and while vibrating thescreen assembly, separating a fourth portion of the plurality offormation cuttings of a fourth size different from the first, second,and third sizes from the drilling fluid with a fourth screen sectionthat comprises a fourth screen mesh size different than the first,second, and third screen mesh sizes.
 4. The method of claim 3, furthercomprising: directing at least one of the third or fourth portions ofthe plurality of formation cuttings through the screen assembly with theseparated liquid to the liquid outlet; and directing the other of the atleast one of the third or fourth portions of the plurality of formationcuttings to the cuttings outlet formed in the screen.
 5. The method ofclaim 1, further comprising directing the at least one of the first orsecond portions of the plurality of formation cuttings at a downwardangle toward the cuttings inlet and away from a perimeter of the screen.6. The method of claim 1, wherein vibrating the screen assemblycomprises: operating a motor to drive a gear or wheel coupled with thescreen assembly; based on driving the gear or wheel, oscillating thescreen assembly with a plurality of springs coupled to the screenassembly.
 7. The method of claim 1, wherein the first screen sectionthat comprises the first screen mesh size is positioned to receive thedrilling fluid that comprises the liquid and the plurality of formationcuttings during separating the first portion of the plurality offormation cuttings of the first size from the drilling fluid with thefirst screen section.
 8. The method of claim 7, wherein rotating thescreen assembly comprises: rotating the screen assembly to position thesecond screen section that comprises the second screen mesh size toreceive the drilling fluid that comprises the liquid and the pluralityof formation cuttings.
 9. The method of claim 1, further comprisingprior to rotating the screen assembly, unlocking the screen assemblyagainst rotation.
 10. The method of claim 1, wherein directing the atleast one of the first or second portions of the plurality of formationcuttings to the cuttings outlet formed in the screen comprises directingthe at least one of the first or second portions of the plurality offormation cuttings to the cuttings outlet that is centered at a centerof the screen assembly.
 11. The method of claim 1, further comprisingdirecting at least a portion of the separated liquid through the screenassembly through the liquid outlet and to an enclosed portion of ahousing that is coupled to the screen assembly.
 12. The method of claim2, further comprising: further rotating the screen assembly; whilevibrating the screen assembly, separating a third portion of theplurality of formation cuttings of a third size different from the firstand second sizes from the drilling fluid with a third screen sectionthat comprises a third screen mesh size different than the first andsecond screen mesh sizes; further rotating the screen assembly; whilevibrating the screen assembly, separating a fourth portion of theplurality of formation cuttings of a fourth size different from thefirst, second, and third sizes from the drilling fluid with a fourthscreen section that comprises a fourth screen mesh size different thanthe first, second, and third screen mesh sizes; directing at least oneof the third or fourth portions of the plurality of formation cuttingsthrough the screen assembly with the separated liquid to the liquidoutlet; and directing the other of the at least one of the third orfourth portions of the plurality of formation cuttings to the cuttingsoutlet formed in the screen.
 13. A method for separating cuttings fromliquid in a drilling fluid, the method comprising: circulating adrilling fluid that comprises a liquid and a plurality of formationcuttings to a screen assembly that comprises a screen, the screencomprising a plurality of screen sections; vibrating the screen assemblyduring circulation of the drilling fluid to the screen assembly; whilevibrating the screen assembly, separating, with the screen assembly, theliquid from the plurality of formation cuttings; while vibrating thescreen assembly, separating a first portion of the plurality offormation cuttings of a first size from the drilling fluid with a firstscreen section that comprises a first screen mesh size; rotating thescreen assembly; prior to rotating the screen assembly, unlocking thescreen assembly against rotation by unlocking a locking assembly thatlocks the screen assembly to a rotation assembly; subsequent to rotatingthe screen assembly and while vibrating the screen assembly, separatinga second portion of the plurality of formation cuttings of a second sizedifferent than the first size from the drilling fluid with a secondscreen section that comprises a second screen mesh size different thanthe first screen mesh size; directing the separated liquid through thescreen assembly to a liquid outlet; and directing at least one of thefirst or second portions of the plurality of formation cuttings to acuttings outlet formed in the screen.
 14. The method of claim 13,wherein unlocking the locking assembly comprises removing a pin insertedthrough a bore formed through a first member attached to a screenassembly and a second member attached to the rotation assembly to unlockthe locking assembly.
 15. The method of claim 13, further comprising:further rotating the screen assembly; while vibrating the screenassembly, separating a third portion of the plurality of formationcuttings of a third size different from the first and second sizes fromthe drilling fluid with a third screen section that comprises a thirdscreen mesh size different than the first and second screen mesh sizes;further rotating the screen assembly; and while vibrating the screenassembly, separating a fourth portion of the plurality of formationcuttings of a fourth size different from the first, second, and thirdsizes from the drilling fluid with a fourth screen section thatcomprises a fourth screen mesh size different than the first, second,and third screen mesh sizes.
 16. The method of claim 15, furthercomprising: directing at least one of the third or fourth portions ofthe plurality of formation cuttings through the screen assembly with theseparated liquid to the liquid outlet; and directing the other of the atleast one of the third or fourth portions of the plurality of formationcuttings to the cuttings outlet formed in the screen.
 17. The method ofclaim 13, further comprising directing the at least one of the first orsecond portions of the plurality of formation cuttings at a downwardangle toward the cuttings inlet and away from a perimeter of the screen.18. The method of claim 13, wherein vibrating the screen assemblycomprises: operating a motor to drive a gear or wheel coupled with thescreen assembly; based on driving the gear or wheel, oscillating thescreen assembly with a plurality of springs coupled to the screenassembly.
 19. The method of claim 13, wherein rotating the screenassembly comprises: moving at least one roller coupled with the screenassembly on a rail, and based on moving the at least one roller,rotating the screen assembly about an axis of rotation.
 20. The methodof claim 13, wherein the first screen section that comprises the firstscreen mesh size is positioned to receive the drilling fluid thatcomprises the liquid and the plurality of formation cuttings duringseparating the first portion of the plurality of formation cuttings ofthe first size from the drilling fluid with the first screen section.21. The method of claim 20, wherein rotating the screen assemblycomprises: rotating the screen assembly to position the second screensection that comprises the second screen mesh size to receive thedrilling fluid that comprises the liquid and the plurality of formationcuttings.
 22. The method of claim 13, further comprising prior torotating the screen assembly, unlocking the screen assembly againstrotation.
 23. The method of claim 13, wherein directing the at least oneof the first or second portions of the plurality of formation cuttingsto the cuttings outlet formed in the screen comprises directing the atleast one of the first or second portions of the plurality of formationcuttings to the cuttings outlet that is centered at a center of thescreen assembly.
 24. The method of claim 13, further comprisingdirecting at least a portion of the separated liquid through the screenassembly through the liquid outlet and to an enclosed portion of ahousing that is coupled to the screen assembly.